small patch for float_to_bits and tetra-rx

ciaby ciaby at
Tue Aug 16 11:11:15 UTC 2011

On Tue, 2011-08-16 at 08:52 +0200, Holger Hans Peter Freyther wrote:
> any numbers for that?
I don't have any hard numbers for that, but consider that before
float_to_bits was using 100% cpu on a atom core and was decoding 2-3
times slower than real-time. Now, it doesn't even pop up in top (less
than 1%) :-D

> yes, I think that is still the plan. I once started trying to do this in
> python but the GNU Radio bindings only allow to control modules, not really do
> processing in python.
Sorry, i didn't explain myself properly... I was planning to write it as
a C module. Have a look at the gr_float_to_uchar module, but instead of
returning a single uchar, it should return uchar[2], where each item of
the array contains 00 or 01. Alternatively, we can pack the two bits
into a single uchar and change how tetra-rx reads it. The second
approach looks cleaner, but it's a bit more invasive.. (it breaks
compatibility with all the previously made dumps).
I have one last question for Harald: which parts of the TETRA protocol
hasn't been implemented yet? I would really to contribute the remaining
bits, and maybe finish the rx part. Low-cost open-source TETRA handset
anyone? :-)


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